In a chemical plant, an operator was in the process of extracting lithium (a highly reactive metal, MP: 180 °C) in a lithium chloride electrolysis vessel when an overflow occurred at approximately 2 p.m. A flaming pool (3 m²) formed on the ground. The molten lithium (450 °C) flowed by gravity along the cell’s wall and entered the basement, damaging the water cooling hoses of the cell’s electrical connections. Water flooded the basement of the electrolysis room and vaporised. This seam was then released outside by the forced ventilation system. The thick cloud of water vapour that had formed above the plant and the odours released by the melting Bakelite in the basement of the electrolysis room raised concern among the residents. The operator, having been slightly burned, was evacuated and the 13 other operators were confined. The operator triggered the internal emergency plan. The emergency services and the neighbouring town halls were notified.

All the lithium and sodium cells were shut down, and the internal firefighters dispersed inert powder on the damaged cell and the flaming pool. Fireproof tarpaulins were used to protect the adjacent cells. The outbreak had been brought under control by the time the fire brigade arrived. The sodium electrolysis cells, which could not be shut down for more than 2 hours for fear of damage (6 hours for lithium cells), were restarted at 4 p.m. in spite of a few renewed flames which were quickly brought under control. The internal emergency plan was lifted at around 4:50 p.m. The accident did not disrupt production operations. The firefighters, equipped with self-contained breathing apparatus, pumped the water that had entered the basement. An employee’s back was slightly burned by water vapour while repairing damaged piping in preparation for the restart of the sodium cells. The restart operation produced chlorine odours which lingered around the plant for one hour. The two injured employees were taken to the nearest hospital, and a press release was issued.

The lithium is drawn out of the electrolysis cell once a day under argon pressure (0.3 bar) from the metal collector after it has been isolated from the cell by closing a valve. Equipped with a cover, the cell is not entirely closed to allow raw material to be added regularly. On the day of the accident, the operator correctly followed the procedure but did not completely close this valve (operational failure). The pressure thus rose toward the cell and caused the molten lithium to overflow.

The lithium electrolysis process is a relatively new control process (commissioned less than 18 months ago) and has resulted in accidents. The operator reminded the operators of the importance of compliance with the filling procedure. It replaced the valves on the three lithium cells with ¼-turn models that have no ambiguity as to their open or closed position. The Inspection Authorities of Classified Facilities required the operator to investigate various avenues to improve safety:

• change of hose technology,
• hose protection,
• installation of an overfill protection device (locking of covers, increasing the height of the cell walls, etc.),
• installation of a gutter along the cell walls to protect possible leakage,
• installation of a water collection system (sewer) in the basement.